Electrostatic precipitator



ELECTROSTATIC PRECIPITATOR Filed April 6, 1948 4 Sheets-Sheet 1 FIG.

INVENTORSl l Rober'f L. Buff BY Elmer G. HHs

Sept. 1, 1953 R. L. BARR ET AL ELECTROSTATIC PRECIPITATOR 4 Sheets-Sheet2 Filed April 6, 1948 301g 29% f2s FIG. 3

FIG. 4

JNVENTORS 'Rober' L. Burr BY Elmer G. Hills ma?? www AtivA Sept. l, 1953R. L. BARR ETAL 2,550,672

ELECTROSTAT IC PREC IP ITATR Filed April 6, 1948 4 Sheets-Sheet .'5

INVENTORS Robert L. Burr 45W Eimer G. Hills Sept l, 1953 R. L.. BARRETAL 2,650,672

ELECTROSTATIC PRECIPITATOR Filed April 6, 1948 4 Sheets-Sheet 4INVENTORS Rober 1 Burr By E\mer G. Hills AH v.

Sept. 1, 1953 ELECTROSTATIC PRECIPITATOR Robert L. Barn Glenview, andElmer G. Hills, Chicago, Ill., assignors, by mesne assignments, to`Vl7est,ingl1ouse Electric "Corporation," East Pittsburgh, Pa., acorporation of Pennsylvania Application April 6, 1948, Serial No. 19,377

(Cl. 18S- 7) 5 Claims.

This invention relates to apparatus for removing particles of foreignmatter from gases by means of electrostatic precipitation and moreparticularly to an improved vprecipitator `unit which is suitable foruse in homes, oiiices and the like for cleaning the air that is to bebreathed.

It has been found `that the operation of `such precpitator units has.been improved by the use of high frequency .energy for ionization.However, a precipitator utilizing a high frequency power supply presentsproblems `in interconnecting the various units because .of power loss incorona on interconnecting cables and the detuning effect of leadcapacities on the high frequency generator. The high voltages .requiredin precipitator units are a further hazard to persons who may come incontact with the precipitator lunit as contact with any portion of thehigh voltage power supply might result in 'shock or serious personalinjury. The fan for causing circulation of air throughthe precipitatoris another source of danger as accidental contact therewith, especiallyby children, might cause serious injury. The positioning of the fan inthe unit can be arranged to eliminate such danger, but the positioningmust be such thata smooth .now of the yair to be cleaned over theionizer and dust collector is providedin order that highly effectiveprecipitation is obtained.

In present precipitator structures, the ionizer and dust collectorarerelatively complicated with the result that precipitators have beenyrelatively expensive. Such collectors used at present are verydifficult to clean, which cleaning is necessary at frequent intervals toprovide satisfactory installations, hot Water pipes are permanentlyconnected to the precipitator and an arrangement is provided whereby thecollector may be hushed with hot water when `the precipitator is dirty.This results in anexpensive and compli- .cated installation, and has notbeen entirely satis- 35 operation of the precipitator unit. In some homeA further object of this invention is to pro- 2 provide an improved`ionizing structure which is of simple construction.

A feature of this invention is the provision of an electrostaticprecipitator in which the high voltage power supply, the ionizerstructure and the collector plates are so positioned that connectingleads are short and a relatively few insulators for the high voltageleads are required.

A further fea-ture of this invention is the provision of a precipitatorstructure in which the components are so arranged that air may becirculated therethrough in a smooth even flow.

A still further feature of this invention is the provision of acollector Astructure which may be made of cardboard or similarinexpensive nsulation material with conducting areas thereon.

Fur-therobjectseatures and advantages of the invention will be `apparentfrom a consideration of the following description taken in connectionwith the accompanying drawings in which:

Fig. 1 is a perspective view of a precipitator unit in accordance withthe invention with parts brokenaway to show the construction;

Fig. 2 is a perspective vieW of the ionizer structure of Fig. l;

Fig. 3 illustrates a modied ionizer structure;

Fig. 4 is `a cross-sectional view of one of the insulating rods of theAionizing structure of Fig. 2 showing the clip for supporting theionizing conductor; d

Fig. 5 is a perspective view of the collector structure of Fig. v1

Figa-6 and? illustrate another embodiment of the collector structure;

Figs. 8 to 11, inclusive, show details of the structure of Figs. 6 and 7Fig. 12 illustrates anarrangement for supporting the collector structureof Figs. 6 to ll in a preciptator unit;

Fig. 13 is aperspective v'iewof still another embodiment of thecollectorstructure.; and

Fig. 14 is a diagramma-tic view showing the electrical .circuits of thecleaner of Fig. l.

In practicing the A*invention there is provided an electrostatic`precipitator .unit including a cabinet which is intheiform of `an endtable or the like. The cabinet in'cludesan ionizing stru"- ture,collector structure, a power supply for the ionizer and collector, and afan for circulating air to be cleaned through the precipitator unit. Thepower supply. is positioned above and adjaent -to the ionizer andcollector so that short leads can be .providedsimplifying the insulationof the leads and .preventing vobjectionable capac- 3 ity loads on thepower supply circuit. The position of the ionizing structure and thecollector structure in the cabinet is such that a steady flow of air canbe provided thereto and also so that the collector structure can beeasily reinoved without moving other components of the precipitatorunit." 'I'he collector structure may be made of cardboard so constructedthat the structure can be folded and shipped or stored in a very smallspace. Certain portions of the cardboard structure are renderedAconducting so that the collector can be energized as will be describedhereinafter.

In the drawings, in Fig. 1 there is illustrated the cabinet or case I inwhich the components of the electrostatic precipitator or gas cleanerare housed. The fan I4 draws air successively through the intakeopenings I5 in the sides and bottom of the cabinet, the ionizingstructure l2, and the collector structure and then forces the cleanedair out through exhaust opening i6. The power supply 22 furnishes highvoltage unidirectional current for exciting the collector structure andhigh frequency high voltage superimposed upon the direct current voltageexisting across the electrodes of collector Il for exciting theelectrodes of the ionizer structure I2. Baiile prevents the ow of airabove the ionizer structure so that lall air being drawn through theapparatus must pass through the ionizing structure where it is ionizedthus causing any particles of dust, pollen or other foreign matter tobecome electrically charged. Collector fits tightly against ionizer I2such that all the air being drawn into the ionizer must go through thecollector where any charged foreign particles are caused to moveperpendicularly to the iiow of air under the forces of the electrostaticiields existing in the collector until said particles strike and adhereto the plates of the collector. The cabinet |0 is provided with aremovable end wall 23 which allows the collector I I to be removed forcleaning or replacement by being drawn under fan |4 through the end ofthe case.

For making electrical contact to the collector and permitting easyremoval thereof, spring conducting means I9 is provided which pressesagainst the top of collector forming an electrical contact to said top,which is one of the terminals of the collector. A second springconducting means |8 presses against collector terminal 24 in the samemanner as the contact I9 so that contact is broken and made successivelyas the collector is removed from and replaced in the case. The fan I4 ismounted directly in front of exhaust opening I6 where it effectivelyprevents the projection of any conducting object through the opening tomake contact with the electrodes of collector |I thereby causingelectrical shock to the holder of said conducting object. As the fanrotates in a direction to exhaust the air it will tend to push anyobject out of the cabinet rather than draw it in. A suitable grille maybe provided over the exhaust opening to further prevent entry of foreignmaterial. By being mounted above the collector II, lthe fan need not bemoved upon withdrawal of the collector.

The power supply 22 may be mounted on the top wall of the cabinetimmediately above the ionizing structure I2 and the collector so thatconnections can be made thereto by relatively short leads. This reducesundesired couplings through the leads and also reduces the number 4 ofhigh voltage insulators required for support-'- ing the leads. Theoscillator tube 2| of the power supply and the low voltage rectifyingtube 20 used in the production of direct current for the oscillatorplate supply from an alternating current power line are located suchthat they can be replaced without opening the power supply box. Theoperation of the power supply 22 will be described more in detailhereinafter.

The ionizing structure I2 is shown in greater detail in Fig. 2. Endplates 33 and 34 are held in position by top and bottom members 3| and'32 respectively. A plurality of separating plates 24 are heldsubstantially parallel to plates 33 and 34 by being spot welded orotherwise fastened to the members 3| and 32. Insulating rods 25 and 26are held by spring clips 35 which are supported on the end plates 33 and34. The rods 25 and 26 are mounted so that they pass through recesses inthe separating plates 24 and are held substantially parallel to top andbottom plates 3| and 32. A plurality of clips 3B support the thinconductor 21 on the rods 25 and 26 so that `the conductor 21 issuspended between and substantially parallel to the conducting plates24. The detailed structure of the clips 36 is shown in Fig. 4. The clipsinclude loops 89 through which the conductor 21 can be hooked. Conductor29 held in place by electrically insulating bushing 28 extends throughtop plate 3| to make contact electrically to conductor 21 and forms oneterminal of the ionizing structure. Conductor 30 electrically connectedto the top plate 3| forms the second terminal of the ionizing structure.One long edge 32a of the bottom plate 32 may be bent upward such that itextends as high as the top of rod 25 and one long edge of top plate 3|may be bent downward such that it extends down as low as the bottom edgeof rod 26. The two bent portions of the plates 3| and 32 form baffleswhich prevent air from being drawn through the ionizing structurethrough paths other than between conductors 21 and nlates 24 where theionization is the most intense.

In Fig. 3 there is shown a second form that the ionizing structure l2may take in which relatively large conductive electrodes 24 are held inposition by members 40 and 4| to which they are spot welded or otherwisefastened. Members 40 and 4| have long edges bent respectively down andup which may be fastened to the baffling edges of plates 3| and 32respectively, The edge of member 4I is indicated by 4| a and is securedto the barile edge 32a by screws 42. The edges o1' member 40 and plate3| do not show in the drawing. Dielectric rods 38 extend throughopenings in the plates 40 and 4| such that they bear against plates 3|and 32 which latter plates prevent their slipping out of the openings inplates 40 and 4|. A plurality of conductive means 31 are held near thedielectric rods 38 by clip means 36 as used in the structure of Fig. 2and illustrated in Fig. 4. Conductor means 39 connects all conductors 31together and to the ionizer terminal 29. The dielectric rods 38 increasethe electrical stress concentration along portions of conductors 31 whena high frequency component of voltage is applied between terminals 29and 30 of the ionizing structure thus increasing the amount ofionization produced. This is disclosed and claimed in the copendingapplication of Elmer G. Hills, Serial No. 731,734, led March 1,9El294'7, now Patent 2,585,777 dated February 12.

The collector structure of Fig. 1 is shown in more detail in'Fig. 5.Collector plates 41 and 48 are supported on top and bottom plates 44 and44a which are fastened to side plates 45 and 45a. The collector plates48 are insulated from the supporting structure by insulator bushing 46.The top and bottom edges of plates 45 and 45a are formed or bent suchthat they are substantially parallel to plates 44 and 44a and theseedges are spot welded or otherwise fastened to the top and bottomplates. Similarly collector plates 41 have their top and bottom edgesbent and fastened to plates 44. Interleaved between plates 41 andinsulated therefrom are plates 48 which are maintained in position bybeing spot welded or otherwise fastened to strips 49 by triangularshaped corners which are bent substantially at right angles to thestrips 49 such that they are substantially parallel to the plates 48.Strips 4Q are maintained in position by the insulating bushings 46 whichhold the strips substantially parallel to plates 44 and 44a. Collectorplates 423 are not as high as plates 41 and are spaced therefrom by adistance greater than the spacing between plates 4B and 41. This isnecessary as high stress concentrations would exist along the relativelysharp edges of plates 48 which would cause electrical arcs to plates 44and 44a although the voltage existing between plates 4l and 48 would beless than the arc over voltage for the spacings of the plates. Anelectrical conductor 24 extends through a hole in plate fifi and throughone of the bushings 46 to make contact with one of the conducting strips4S thus forming one terminal of the collector structure. The otherterminal is formed by the supporting structure. The connection of thecollector in the precepitator unit is illustrated in Fig. l.

A modied collector structure is illustrated in Figs. 6 to l2 which is ofinexpensive construction so that it can be disposed of after use.Disposable collector structures are disclosed and claimed in thecopending application of Robert L. Barr, Serial No. 719,893, filedJanuary 2, 1947. The structure of Figs. 6` to l2 is a simplifiedstructure which includes a top plate 14, two sets of collector plates leand 1l, end plates 19 and a bottom plate 86. The top plate or supportingmember 14 is held by staples, glue, or other means to one of the edges15 of each of the plates l5 which edge is folded at substantially rightangles to the main portion of the plate 16 when the collector is inopened condition. In a similar manner the top plate 14 is held to one ofthe edges 1S of each of two end plates 19, and is held to the foldededge Se of each of the plates 11 which plates are interleaved betweenthe plates 'it of the nrst set. In a similar manner a bottom plate S6 isfastened to the, other folded edge of each of the plates 1S, 11 and 19.

The top plate 14 is rendered conducting over a large portion 82 thereof`and includes a narrow conducting strip 3'! which is insulated from theconducting portion 82 (Fig. 8). The end plates 'i9 are renderedconducting over a portion substantially ccextensive with the portion 82of the top plate as shown in Fig. l0. The plates 16 of the llrst set maybe identical with thel end plates 19 or may be of the construction shownin Fig. 9 in which the plates l are shorter than the other plates beingsubstantially coextensive with the conducting portion 82 of the topplate. In this case the plates are rendered conducting over their entirearea. The plates11of the second set are rendered electrically conductivethroughout a substantial portion of their areas, as shown by 8| in Fig.l1, buit are left Vnon-conducting throughout the non-shaded areas 80,8'3 and 84. Plates l'i are so oriented in the structure that-theconducting' portion 85 at the top of each plate contacts the strip 31 ofthe top plate which is rendered conducting. The strip t1 forms oneterminal of the collector structure. Insulated portions 83 and S4 alongthe edges of plates 11 insulate the conducting portions 8i from theconducting portion 32 of the top plate 'i4 and, therefore, from plates'le and 19. The plates 19 (Fig. 10) have insulated portions 9@ such thatthe folded portions 85 of the outer two plates 11 will not provide shortcircuits to the end plates 18 through which an electrical dischargemight take place.

.fl-.ll the plates of the entire collector structure can be made ofcardboard, or some similar ma-` terial sufficiently stiil to support itsown weight,

which has been rendered electrically conductiveV as by a printingprocess, by having metallic foil fastened to at least one side, by achemical process, or by any other means. The insulating material maypreferably be rendered nreproof and non-hydroscopic so that theinsulating properties thereof are improved. The lines along which theedges of plates 15, 11 and 19 are folded may be flexible enough to allowthe entire structure to collapse as indicated in Fig. 'l in which thestructure is in a partialv state of collapse. Such a collapsiblecollector struc ture could be held in an open condition by the t shapeof the precipitator case and by runners S3 as illustrated in Fig. 1. Toprevent bending of the collector plates when they are made oi light.inexpensive material to form a disposable structure, supporting endstructures el?, as illustrated in Fig. l2, which are made of insulatingmaterial can be used. The structures invclude a plurality of stampedsheets 9i secured together by spacers '$32. The sheets have toothededges including grooves 93 which support ther edges of the collectorplates and points 94 for ease in positioning the end structuresrelative. to the plates. By providing openings 95 in the sheets, thepaths along the sheets for leakage currents between the plates areincreased. lThe end structures do not materially offset the free new ofair through the collector structure. In. Fig. l2 there is shown springclips 9E which may be provided for holding the collector structure inposition in the case of the precipitator unit. The clips are positionedin recesses Q1 in the side walls of the case and the ends thereof mayengage the sheets 9i of the end structure atl. By pressing the ends ofthe clips into recesses E31 the clips may be releasedfto permit removalof the collector structure for cleaning or re placing.

rlhe manner of making electrical connection to the disposable collectorstructures is also shown in Fig. l2. In this ligure the spring conductormeans I e is shown hinged so that the end thereof contacts theconducting'strip 31 of the top plate 'E4 of the collector structure. Anysuitable means can be provided for alternatively securing the hingedportion of the conductor in the positions shown in Figs. 1 and l2.

Another embodiment of the collector structure is shown in Fig. 13 inwhich two conductive sheets iii and t2 may be rendered conductive. Thesheets may be made of paper,. plastic, screen wire `or other materialwhich can 'be 'rendered electrically conducting. insulating member 53,

which may be corrugated paper,'plastic or other insulating material,maintains a substantially constant separation between sheets and 52throughout the areas of said sheets while allowing air passages betweensaid sheets. The edges of sheets 5| and 52 are brought out and connectedto terminals 54 which are the terminals of the collector structure. Thestructure lends itself to economy of manufacture by its ability to berolled into a shape as shown in Fig. 13 out of a sheet constructedsomewhat like a sandwich. The air channels existing between sheets 5|and 52 and portions of insulating material 53 are substantially parallelto the axis of the structure into which the collector is rolled.

In the electrical circuit of Fig. 14 standard alternating current poweris provided for the precipitator unit from the local power line by plug55. The power is brought in through interlock switch 56 by means ofconductors 59 to low voltage power supply means 51 as well as toelectric fan means |4. The interlock switch may be arranged tode-energize the unit when the end 23 of the case Il) is removed. Thepower supply 5l provides heater and plate power for electron dischargevalve 2| and may be of standard construction. A tank circuit composed ofinductor 6| and capacitor 62 is connected in the plate circuit of valve2|. Magnetically coupled to inductor 5| is the high voltage secondarycoil 66. Electrostatically coupled to the high voltage coil 6E isconductor 65 which provides a feedback path from the plate to the gridcircuit of valve 2| so that an electrical oscillator circuit isprovided. Grid leak resistor 64 provides a direct current path to thecathode from the grid of the oscillator to prevent blocking of the grid.Because the conductor 55, the coil 66 and the insulation between themform an electrical condenser through which the feedback energy forexciting the grid of the oscillator passes, a phase shift occurs whichdecreases the amplitude of oscillation. Condenser B3 connected betweenthe grid and cathode of oscillator 2| corrects for this phase shift.Although the valve 2| is illustrated as a tetrode having a screen gridto which potential is applied through resistor 6|), it is obvious thatother types of valves can be used.

The high voltage appearing across the terminals of coil 6&5 due to thecoupling of the coil to the tank coil 6| of the oscillator is appliedbetween the cathode of rectifier 68 and one electrode of the collectorstructure. The anode of rectier 68 is connected (through ground) to theother terminal of the collector structure such that the rectier rectiesthe output of coil 66 thus applying a unidirectional, pulsatingelectrical current to the collector structure. Inductor 61 ismagnetically coupled to coil 66 such that the proper high frequencyvoltage is induced in it to heat the cathode of rectier 68. Because ofthe electrical capacitance of the collector and the high frequency ofthe output voltage of coil 5t the voltage appearing between theelectrodes of the collector is substantially unidirectional and ofconstant amplitude. The use of the collector as the lter condenser ofthe power supply is disclosed and claimed in the copending applicationof Elmer G. Hills, Serial No. 642,473, i'lled January 21, 1946. Oneterminal ID of the ionizing structure is connected by means of a. groundpath to the grounded side of the collector structure. The other terminal13 of the ionizer is connected by means of short, direct conductor B9 tothe cathode of the rectier 68. Because of this connection the voltageapplied to the terminals of the ionizing structure is the sum of thesubstantially direct current voltage existing across the collector andthe alternating current voltage of high frequency existing across coilIncreased ionization due to the combination of direct current and highfrequency alternating current voltages being applied to the ionizingstructure is thus realized. At the same time, high intensity constantelectrostatic fields are caused to exist between the plates of thecollector structure.

It is seen from the above that we have provided an improved precipitatorunit which is of small and compact construction suitable for use in ahome. The specific arrangement of the components results in a veryefcient unit. The use of the collector as the power supply filterresults in decrease in the cost of the unit. The improved collectorstructures simplify the maintenance of the precipitator unit, thedisposable collectors eliminating the difficult cleaning of thecollectors which was formerly required. The structure of the disposablecollectors is such that they can be inexpensively constructed and foldedfor storage and shipment in a relatively small space.

In the following claims the word collector shall mean any structure intowhich the gas containing electrically charged particles of foreignmatter is drawn and upon the electrodes of which these particles aredeposited; the word ionizer shall mean any device which causes the gasbeing drawn through it to become ionized such that particles of foreignmattei' passing through it will become charged; the word fan shall beunderstood to designate any means for causing a gas ilow through theprecipitator unit; the word case shall be understood to mean anysuitable covering or cabinet for housing the gas cleaning apparatusincluding the various brackets or other means for maintaining therelative positions of the components of the apparatus; the words powersupply shall be understood to mean the equipment for generating theexciting voltages for the ionizer and collector which itself may receiveenergy from a source external to the gas cleaning apparatus.

While certain embodiments of our invention have been described for thepurpose of illustration, it should be understood that the invention isnot limited to the exact circuits and arrangements of apparatus hereindescribed, as modifications thereof may be suggested by those skilled inthe art without departure from the essence of the invention as definedin the appended claims.

We claim:

1. An electrostatic gas cleaning apparatus comprising a case, anionizer, a collector, a fan, and a power supply. said case having top,bottom, end, and side walls, one of said end walls being removable andhaving an exhaust opening in the upper portion thereof, intake openingssaid case adjacent the end opposite said one end, said ionizer and saidcollector being supported in said case on said bottom wall intermediatethe ends thereof with said ionizer adjacent said intake openings andsaid collector adjacent said exhaust opening, said fan being supportedfrom said top wall of said case in front of said exhaust opening andarranged to draw gas through said intake openings of the case, andthrough said ionizer and said collector and exhaust said gas throughsaid exhaust opening, said power supply being supported by said top wallof said case above said ionizer and said collector and includingconductor means projecting therefrom, said collector being removablefrom said case when said one end wall is removed and having terminalsthereon adapted to engage said conductor means so that connections tosaid collector are automatically made and broken when said collector isplaced in said case and removed therefrom.

2. Apparatus in accordance with claim 1 in which said collector isdisposable and includes a plurality of plates made of material which issufciently stiff to support the weight thereof, means for securing saidplates together to form a boxlike structure including a plurality ofplates which are substantially evenly spaced, said securing rneans beingsuciently flexible to allow said collector to collapse so that saidcollector forms a ilat structure.

3. Apparatus in accordance with claim 1 in which said collector includesa plurality of plates made of insulating material which is sufficientlystiff to support the weight thereof, said plates including a supportingplate and rst and second sets of plates supported therefrom andextending at right angles thereto, plates of said rst set beinginterleaved between said plates of said second set with said plates ofboth sets being substantially evenly spaced, said plates of said firstset being rendered conducting throughout a portion of their areas, saidplates of said second set being rendered conducting throughout a portionof their areas, said supporting plate being rendered conducting on twoportions thereof with one conducting portion contacting said conductingportions of said first set of plates and the other conducting portioncontacting said conl0 ducting portions of said second set of plates,said conducting portions of said supporting plate forming said terminalsof said collector.

4. Apparatus in accordance with claim l in which said collector includesa plurality of plates made of relatively thin material, said platesbeing substantially evenly spaced, and including end structuresincluding a plurality of spaced insulating sheets extending at rightangles to said. plates and having toothed edges with alternate pointsand grooves spaced to correspond to the spacing of said plates, said endstructures engaging said collector with said grooves determining theposition of said plates.

5. Apparatus in accordance with claim 1 in which said collector isdisposable and includes a plurality of plates made of insulatingmaterial which has been rendered reproof and non-liy droscopic with saidplates being rendered conducting over certain portions thereof.

ROBERT L. BARR.

ELMER G. HILLS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 670,169 Allen Mar. 19, 1901 1,992,974 Thomson Mar. 5, 19352,233,639 Pegg Mar. 4, 1941 2,449,681 Wilson Sept. 21, 1948 2,486,520Dahlman Nov. 1 1949 2,528,842 Penney Nov. 7, 1950 FOREIGN PATENTS NumberCountry Date 360,119 Germany Sept. 29, 1922

